Optical lenses have for centuries been one of the scientist's major tools. The majority of prior art lenses operate by either focusing light using curved surfaces or by means of diffraction on a surface corrugation (diffractive lenses). The limitations of both types of lenses are well known. No lens can focus light onto an area smaller than a wavelength squared (in the material). However, recently in J. B. Pendry, Negative Refraction Makes A Perfect Lens, Phys. Rev. Lett. 85 (18), 2000, p. 3966, it was theoretically predicted that a slab of material exhibiting a negative refractive index (also known as a left-handed material) could provide a resolution significantly exceeding that of any lens designs known to date. Lenses that might be designed after Pendry's theory have become known as “perfect lenses”.
Even though later it was shown (see, for example, [R. W. Ziolkowski, Phys. Rev. E., 64, p. 056625 (2001)]) that Pendry made some errors in his original analysis [J. B. Pendry, Negative Refraction Makes A Perfect Lens, Phys. Rev. Lett. 85 (18), 2000, p. 3966], Pendry's conclusion still holds: A negative refractive index (NRI) flat slab indeed can act as a lens having subwavelength resolution (see, for example, [J. T. Shen and P. M. Platzman, Appl. Phys. Lett., 80 (18), p. 3286, May 2002; S. A. Cummer, Appl. Phys. Lett., 82 (10), p. 1503, March 2003]). The basis of such a counterintuitive effect is that an NRI slab focuses not only propagating waves (as does a normal lens) but also evanescent waves. The exemplary illustrative FIG. 1 drawing shows schematically the difference in transmission of the image through a “normal” material slab (i.e. with n(ω)>0) (FIG. 1a) and an NRI material slab (FIG. 1b).
NRI material does not exist in nature, so only artificial materials may exhibit a refractive index n(ω)<0. In other terms, the NRI material must exhibit both negative magnetic permeability and negative dielectric permittivity for at least a large enough wavelength range: ∈(ω)<0, μ(ω)<0. Such materials were predicted and theoretically analyzed by Veselago [V. G. Veselago, Sov. Phys. Usp., 10, p. 509 (1968)]. However, it took about 30 years before Pendry and coworkers proposed any practical designs for a material that would exhibit NRI [Pendry, J. B., et al., IEEE Trans. Microwave Theory and Technology, (1999) 47 (11)]. In this paper, Pendry predicted that an array composed of conducting, split ring resonators (SRRs) (as shown in FIG. 2), could mimic the response of a magnetic material and, in particular, would have a well-defined region of negative permeability over a band of frequencies in the microwave regime. Pendry's SRR array was realized and experimentally tested by David Smith, et al., [Smith, D. R., et al., Phys. Rev. Lett., (2000) 84 (18), 4184-4187]. Negative refraction of microwaves incident on the array was demonstrated [Shelby, R. A., et al., Science, (2001) 292, 77-79].
Although it is widely believed that the first study of such media was done by Veselago [V. G. Veselago, Usp. Fiz. Nauk, vol. 92, pp. 517-526, 1967], it is not strictly true. For example, Mandel'shtam as early as in 1945 [L. I. Mandel'shtam, “Lectures On Certain Problems Of Oscillation Theory: Lecture 4”, in Polnoe Sobraniye Trudov. Leningrad: Izdat, 1950, vol. 5, Akad. Nauk SSSR, pp. 461-467; L. I. Mandel'shtam, Zh. Eksp. Teor. Fiz., vol. 15, pp. 475-478, 1945] referred to a 1904 paper of Lamb [H. Lamb, “On group-velocity,” in Proc. London Math. Soc., vol. 1, 1904, pp. 473-479], who may have been the first person to suggest the existence of backward waves (his examples involved mechanical systems rather than electromagnetic waves). In 1905, Pocklington [H. C. Pocklington, Nature, vol. 71, pp. 607-608, 1905] showed that in a specific backward-wave medium, a suddenly activated source produces a wave whose group velocity is directed away from the source, while its phase velocity moves toward the source.
In [Podolskiy, V., et al., J. Nonlinear Optical Physics & Materials, (2002) 11 (1), 65-74] it was suggested theoretically that certain nanowire composites would be a viable basis for thin-film negative index materials (NIMs) for the visible and near infrared (IR) spectral ranges. Numerical simulations showed that plasmon resonance modes were created around distributed dipole needles arranged in parallel pairs [Podolskiy, V., et al., J. Nonlinear Optical Physics & Materials, (2002) 11 (1), 65-74]. Currents induced in the wire pairs contribute to the resonant conditions, which in turn account for the negative refractive index. Independently, the same (or very similar) idea was proposed by Panina et al. [L. V. Panina et al., Phys. Rev. B, 66, p. 155411 (2002)]. FIG. 3a gives a schematic drawing of such a material, while FIG. 3b shows the spectral dependences of the real and imaginary parts of the effective dielectric permittivity and magnetic permeability that were theoretically predicted by Panina, et al. These predictions apply for the electromagnetic wave propagation along the k direction, shown in FIG. 3a, for a material having the polarization such as the electric and magnetic field vectors of the electromagnetic wave coincide with the E and H directions showed in FIG. 3a. However, in none of these disclosures the possible method of fabrication of such a material has been proposed. The main problem with optical and IR frequencies is to create a material that possesses negative magnetic permeability.
NRI materials hold enormous promise for many applications. In addition to imaging devices, where the applications are obvious, such materials would enable many other applications. In the microwave region (and potentially in optical spectral region as well) for example, a medium that focuses waves when other materials would disperse them, and vice versa, will be useful in improving delay lines, couplers, duplexers, antennas, and filters. T. Itoh et al, have theoretically demonstrated the possibility of a new, highly compact forward-wave directional couplers based on artificial, left-hand transmission lines with microstrip components [Liu, L., et al., J. Appl. Phys., (2002) 92 (9), 5560-5565]. Eleftheriades [Ayer, A. K., and Eleftheriades, G. V., IEEE International Microwave Symposium Digest, (2002), pp. 1067-1070; Grbic, A., and Eleftheriades, G. V., J. Appl. Phys., (2002) 92 (10), pp. 5930-5935] claimed that artificial constructs of this kind (also called metamaterials) offer large operating bandwidths and, being planar, would readily support two-dimensional wave propagation, making them highly suitable for RF/microwave devices and circuit applications. In particular, opportunities exist for compact devices capable of beam steering and microwave focusing, as well as solid-state filters and miniature ‘backward’ antennas.
Many believe that prospects for NRI materials are greatest in the IR/visible region. Such materials, if successfully created, will enable new types of band-pass filters, modulators, antennas, and other light manipulating devices. Shalaev [Podolskiy, V., et al., J. Nonlinear Optical Physics & Materials, (2002) 11 (1), 65-74] predicted that the possibilities for nonlinear waves and devices like optical solitons could revolutionize optoelectronics. NRI materials could hugely improve technologies for biomedical imaging and nanolithography. Opto-magnetic material (as opposed to normal magneto-optic materials) is a term introduced by Panina [L. V. Panina et al., Phys. Rev. B, 66, p. 155411 (2002)]), meaning a material exhibiting magnetic permeability at optical frequencies. A material exhibiting a degree of permeability at optical frequencies, but not enough to create a negative refractive index, is predicted to have applications in a new generation of magnetic field and electrical current sensors and in tunable optical elements (such as tunable filters, modulators, lasers, etc.). Despite numerous theoretical studies devoted to NRI materials during the last several years, no such materials have been manufactured for optical and IR wavelengths.
It is an object of the present exemplary illustrative non-limiting implementation to provide the practical design of NRI materials for the visible and/or infrared spectral range that will exhibit negative values of the refractive index at least for some directions of light propagation through said material for at least some polarization states of said light, over at least some interval of wavelengths of said light. It is a further object of the present exemplary illustrative non-limiting implementation to provide the practical design of the NRI that would exhibit negative values of the refractive index for any direction of light propagation through said material for at least some polarization states of said light over at least some wavelength range. It is another object of the present exemplary illustrative non-limiting implementation to provide a practical design of NRI material that would exhibit a negative refractive index for at least some directions of light propagation for any polarization state of said light over at least some wavelength range. It is a further object of the present exemplary illustrative non-limiting implementation to provide a practical design of the NRI material that would exhibit a negative refractive index for any directions of light propagation for any polarization state of said light over at least some wavelength range. Further, it is an object of the present exemplary illustrative non-limiting implementation to provide a practical design of the opto-magnetic material that will exhibit magnetic permeability values substantially different from unity for at least some directions of light propagation through the material, for at least some polarization states of said light over at least some wavelength interval within the infrared wavelength range. It is also an object of the present exemplary illustrative non-limiting implementation to provide several practical methods of fabrication of NRI and/or opto-magnetic materials of present exemplary illustrative non-limiting implementation.
According to the first exemplary illustrative non-limiting implementation, a negative refractive index material exhibiting negative refraction for at least some directions of light propagation through said material, for at least some polarization state of said light over at least some wavelength range within the IR can be realized by creating a structure consisting of a several lattices of wire pairs such that in each of these said metal wire lattices, wire pairs are “aligned” such that both the metal wire directions and the planes of wire pairs are essentially parallel to each other, while the wire pairs belonging to different sublattices have either wire directions or planes of wires not parallel. The metal wire pairs in each of said sublattices can be either spatially ordered or disordered (i.e., random). The principle difference between the NRI, or opto-magnetic material of the present exemplary illustrative non-limiting implementation and the prior art material, as disclosed, for example, in [Podolskiy, V., et al., J. Nonlinear Optical Physics & Materials, (2002) 11 (1), 65-74] and [L. V. Panina et al., Phys. Rev. B, 66, p. 155411 (2002)], is that in prior art material the wire pairs were distributed completely randomly either in the plane (two-dimensional case) or in space (three-dimensional case), while in the material of the present exemplary illustrative non-limiting implementation the “randomness” of the material is substantially reduced, which can lead (as will be shown later) to greatly improved performance of the material.
According to the first aspect of the first exemplary implementation of the present exemplary illustrative non-limiting implementation, the NRI and/or opto-magnetic material comprises the film having a thickness in the range of 1 μm to 1000 μm and consisting of a single lattice of metal wire pairs extended perpendicular to the film's plane. We shall denote such a material as 1D (one dimensional) material in the future discussion. Such a material will have strongly anisotropic dielectric permittivity and magnetic permeability tensors at wavelengths around resonances in the metal wire pairs. It can exhibit negative refractive index only for electromagnetic waves propagating in the plane of the film in the direction perpendicular to the plane of the wire pairs and in a small cone of angles around this direction. This will occur over some wavelength range and the polarization range of the electromagnetic wave FOR which the electric field vector of said wave is parallel to the wire direction (i.e, perpendicular to the film plane transverse magnetic (TM) polarization). This type of anisotropy belongs to the class of materials called “indefinite” materials (since different elements of dielectric permittivity and magnetic permeability tensors will have different signs). Further, the diameters of the wires can optionally be coherently modulated along the film depth so the effective refractive index of the film will be modulated across the film depth. In this manner, a waveguide structure can be created in the plane of the film, which can have a number of important applications. Still further, such a material would exhibit values of magnetic permeability substantially different from unity in some part of the IR spectral range for all the electromagnetic waves propagating through said material in directions lying in the plane of the wire pair plane and having such a polarization state that the magnetic field vector of the electromagnetic wave is directed perpendicular to the planes of wire pair. This will allow the material be used as an opto-magnetic composite for a number of directions, which is lead to applications in light modulators and sensing of physical parameters.
According to the second aspect of the first exemplary implementation of the present exemplary illustrative non-limiting implementation, the NRI and/or opto-magnetic material comprises the film having a thickness in the range of 1 μm to 1000 μm consisting of two lattices of metal wire pairs extended perpendicular to the film's plane, and additionally the planes of wire pairs in these lattices are perpendicular to each other. Such a material is denoted a 2D (two dimensional) material in the succeeding discussion. Such a material will still have strongly anisotropic dielectric permittivity and magnetic permeability tensors at the wavelengths around resonances in metal wire pairs, but the anisotropy will be substantially reduced with respect to the 1D material. It can exhibit negative refractive index for electromagnetic waves propagating in any direction in the plane of the film for the polarization of said electromagnetic wave such that the electric field vector is directed perpendicular to the film plane (i.e., the TM polarization, as in 1D case). This type of anisotropy also belongs to the class of materials called “indefinite” materials (since different elements of dielectric permittivity and magnetic permeability tensors will have different signs), but, unlike 1D case where in the coordinate system where dielectric permittivity and magnetic permeability tensors are diagonalizable, it has one negative and two positive tensor elements, 2D material would exhibit two negative and one positive tensor elements. Further, the diameters of the wires can be coherently modulated along the film depth so the effective refractive index of the film will be modulated across the film depth. In this way, a waveguide structure can be created in the plane of the film. For light with such a waveguide mode, the refractive index of the core and/or cladding would be negative for any direction of propagation. Such a structure can have a number of important applications. Further, such a material would exhibit values of magnetic permeability substantially different from unity in some part of the IR spectral range for all the electromagnetic waves propagating through said material in any directions having a polarization state such that the magnetic field vector of the electromagnetic wave is parallel to the plane of the film (i.e., TM or p-polarized waves). Alternatively, such a material would exhibit values of magnetic permeability substantially different from unity in some part of the IR spectral range for all polarizations of electromagnetic waves incident within some cone of angles around the normal incidence direction. This would allow the material to be used as an opto-magnetic composite for a number of directions, which is predicted to find applications in light modulators and in the sensing of physical parameters.
According to a third aspect of the first exemplary illustrative non-limiting implementation, the NRI and/or opto-magnetic material comprises a film having a thickness in the range of 1 μm to 2000 μm consisting of three or more lattices of metal wire pairs, at least one of them extended at some angle with respect to the film's plane. Such a material is denoted as 3D (three dimensional) material in the succeeding discussion, despite the fact that there may be more than three lattices of metal wire pairs. Depending on configuration, such a material will either exhibit weak uniaxial or biaxial anisotropy of the dielectric permittivity and magnetic permeability, or will be completely isotropic at the wavelengths around resonances in the metal wire pairs. 3D material can exhibit negative refractive index for the electromagnetic waves propagating in any direction with respect to the film for any polarization of said electromagnetic wave at least over some wavelength band within the IR range. However, the values of the refractive index can be different in different propagation directions or for different polarizations, while all being negative at some spectral range. Still further, such a material would exhibit values of magnetic permeability substantially different from unity in some part of the IR spectral range for all the polarizations of electromagnetic waves propagating through said material in any direction, i.e., such a material will be an isotropic or omnidirectional opto-magnetic material.
According to the second exemplary illustrative non-limiting implementation, the negative refractive index material of the first exemplary illustrative non-limiting implementation can be realized as a assembly of wire pair lattices, wherein said wires are composed of a multilayered, metal-dielectric structure. The structure of each wire in such a material will be identical and composed of layers of metal(s) and dielectrics. Such a structure can provide better opportunity for engineering control over the shape and spectral position of dielectric permittivity and magnetic permeability resonances by means of better control over the plasmon modes. Particularly, the quality of the resonances can be substantially improved by creating so-called anti-symmetric plasmon modes in the wires, which is known to provide lower losses and a higher quality of resonances. This, in turn, will lead to the increase of the absolute value of electric polarizability and magnetic susceptibility of each wire pair and through that to lower values of dielectric permittivity and magnetic permeability of the NRI and/or opto-magnetic material of the present exemplary illustrative non-limiting implementation. It should be noted that such a wire structure would considerably improve the NRI and/or opto-magnetic material over prior art designs as described in, for example, in [Podolskiy, V., et al., J. Nonlinear Optical Physics & Materials, (2002) 11 (1), 65-74] and [L. V. Panina et al., Phys. Rev. B, 66, p. 155411 (2002)]. Further, said wire pairs can be embedded in the semiconductor or dielectric host. In such a case it is necessary that said semiconductor and/or dielectric material should be sufficiently transparent at the wavelengths of permittivity and permeability resonances of said wire pair structures. It is also desirable that the refractive index of refraction of said host material should be low enough to be able to achieve negative values of the refractive index of the film. Alternatively, the host material can be a semiconductor or semiconductor/dielectric structural material with as low a refractive index as can be achieved artificially by means of the modification of the material structure.
According to the third exemplary illustrative non-limiting implementation, a method is provided for the fabrication of the NRI and/or opto-magnetic material of the first two illustrative implementations. According to one non-limiting illustrative exemplary arrangement, a 1D or 2D material can be fabricated from a semiconductor wafer by forming a porous semiconductor structure (where pores are straight and non-branching) by means of electrochemical or photoelectrochemical etching technique with the subsequent filling of said pores with metal or by the coating of the pore walls by a metal-dielectric multilayer. Pore cross sections can be modulated at least along part of their depths while other parts are left unmodulated, or the entire depths can be modulated. With such a method, NRI and/or opto-magnetic material not only can be fabricated for scientific research purposes, but also can be fabricated relatively simply and inexpensively, leading to more immediate commercial applications.
Said metal wires dimensions and positions in the film will be defined by pore sizes and positions. Such a structure can be fabricated, for example, by forming a layer of porous semiconductor by means of electrochemical etching of a single crystal semiconductor wafer as deeply as necessary. Pores formed by such a process will serve as hosts for the metal or metal-dielectric structure of said wires, while the semiconductor host will serve as the medium in which said wires are embedded. Modulation of the cross sections of the wires can be achieved by means of the modulation of the pore diameters along their depths by modulating the electrochemical etching parameters during the etching process. For example, the parameters available for modulation include the current density, illumination intensity or others known to those skilled in the art. Said semiconductor material can be silicon (P-type doped or N-type doped), gallium arsenide, indium phosphide or any other material shown to form straight pores during electrochemical etching in a suitable electrolyte and under suitable conditions. The pore filling or covering of the pore walls by metal or metal/dielectric multilayers can be achieved by electroplating techniques or by a Chemical Vapor Deposition technique (preferably by the Atomic Layer Deposition variation of CVD), or by any other deposition or growth process known to those skilled in the art, such as sputtering or evaporation.
This specification also discloses exemplary, non-limiting illustrative methods for manufacturing of NRI and/or opto-magnetic material. According to the one aspect of the present exemplary implementation, NRI and/or opto-magnetic material of the first exemplary implementation can be produced by:                selecting a semiconductor wafer having first and second surfaces wherein said first surface is substantially flat,        producing starting points for etching on the first surface of the semiconductor wafer,        producing a porous layer in said wafer starting from the first surface, and        filling the pores with at least one layer of appropriate metal.The porous layer can be formed by means of electrochemical etching of said semiconductor wafer in acidic electrolyte. The etching method may include connecting the substrate as an electrode, contacting the first surface of the substrate with an electrolyte, setting a current density (or voltage) that will influence etching erosion, and continuing the etching to form said pores extending to a desired depth perpendicularly to said first surface (as would be desired for the 1D or 2D material of the first exemplary illustrative non-limiting implementation) or at some angle defined by the crystallographic orientation of the semiconductor wafer (as would be needed for the 3D material of the first exemplary illustrative non-limiting implementation). Said semiconductor wafer can be, but is not limited to, a silicon wafer. Etching starting points (commonly called “etch pits”) can be formed as depressions on the first surface of said wafer to control the locations of the pores to be formed in the electrochemical etching process. Said etch pits can be formed by means of applying a photoresist layer on the first surface of the semiconductor wafer, photolithographically defining the pattern of openings and chemically or reactively ion etching the etch pits through said openings. Alternatively, said etch pits can be formed by depositing (by means of chemical or physical vapor deposition, thermal oxidation, epitaxial growth, sol-gel coating or any other technique known to those skilled in the art) a material layer with different chemical properties than that of the substrate, applying a photoresist layer on the top of said material, photolithographically defining the pattern of openings in the photoresist layer, transferring said patterns into said layer by means of chemical or reactive ion etching and transforming the resultant pattern into a corresponding etch pit pattern by means of chemical or reactive ion etching. Said layer of material with different chemical properties than that of the substrate wafer may then be removed by means of chemical etching, reactive ion etching or any other method known to those skilled in the art.        
More specifically, said semiconductor wafer can be an n-doped, <100> orientated silicon wafer. In this case, the electrolyte can be an HF-based aqueous acidic electrolyte. Alternatively, the electrolyte can be an HF-based organic electrolyte. Alternatively, said semiconductor wafer can be a p-doped, <100> orientated silicon wafer. The electrolyte in this case may be HF-based organic electrolyte. The electrolyte may contain hydrofluoric acid in a range of 1% to 50%, but preferably 2 to 10% by volume. A second surface of the substrate wafer that lies opposite the first surface may be illuminated during electrochemical etching. The electrolyte may additionally contain an oxidation agent, a hydrogen reducing agent (e.g., selected from the group of chemicals consisting of mono functional alkyl alcohols, tri functional alkyl alcohols), a viscosity increasing agent, a conductivity-modifying agent, and/or other organic additives. Electrochemical process parameters such as current density, applied voltage, and illumination intensity can be kept constant during the pore formation process. Alternatively, said electrochemical process parameters can vary in a predetermined fashion during the pore growth process to provide the pores with needed modulation in cross-sections, or may be varied monotonically with pore depth to keep the pore diameter constant. As a further alternative, said semiconductor wafer can be of material chosen from the full possible range of alloys and compounds of zinc, cadmium, mercury, silicon, germanium, tin, lead, aluminum, gallium, indium, bismuth, nitrogen, oxygen, phosphorus, arsenic, antimony, sulfur, selenium and tellurium. The electrolyte may be an acidic electrolyte with the acid suitably chosen for pore formation in the particular semiconductor material.
Said filling of the pores with appropriate metal can be done by means of the electroplating process. It should be noted that by electroplating process the metal “multilayer” can be formed by changing the composition of the electrolyte during electroplating process and/or changing the electroplating process parameters, e.g. applied current density. The metal used to fill the pores can be Au, Ag, Al, Cu, Ta, Ti, Co, Ni, Fe, Pt or it can be a metal alloy. In an electroplating process, complete voidless filling of the pores and formation of a metal axial “multilayer” is possible only if the pores are filled from the bottom up. This nonlimiting, illustrative method of NRI and/or opto-magnetic material fabrication is possible only if no insulating material or layer covers the pore walls. Alternatively, the pores can be substantially filled by an electro-less plating process. In the case of electroless plating, no metal “multilayer” formation is possible from the same chemical bath. Other metal deposition processes (such as various modifications of Chemical Vapor Deposition techniques) are also possible. It should also be noted that, after both the electroplating and electroless-plating processes, some excessive metal could be formed on the first surface of the semiconductor wafer, which may degrade the performance of the NRI and/or opto-magnetic material. Said excessive metal can be removed from the first surface of the semiconductor wafer by a chemical-mechanical polishing technique or any other removal technique known to those skilled in the art.
According to a further illustrative non-limiting method of manufacturing, an NRI and/or opto-magnetic material of the first exemplary implementation of the present exemplary illustrative non-limiting implementation can be produced by:                starting with a semiconductor wafer having first and second surfaces, wherein said first surface is substantially flat,        Producing etch starting points on the first surface of the semiconductor wafer,        producing a porous layer in said wafer starting from the first surface,        removing the un-etched part of said wafer at the distal ends of the pores, and        filling the pores with metal.        
The porous layer can be formed as was described in relation to illustrative methods of manufacturing an NRI and/or opto-magnetic material given previously.
Removal of the unetched part of the wafer can be performed by means of grinding, polishing, chemical-mechanical polishing, chemical etching, reactive ion etching or any other method known to those skilled in the art.
Said filling of the pores with appropriate metal can be done by means of an electroplating process. It should be noted that, by means of an electroplating process, an axial metal “multilayer” can be formed by changing the composition of the electrolyte during the electroplating process and/or changing the electroplating process parameters, e.g., the applied current density. The metal filling the pores can be Au, Ag, Al, Cu, Ta, Ti, Co, Ni, Fe, Pt or In, or it can be an alloy of any combination of these metals. In an electroplating process, complete voidless filling of the pores and formation of an axial metal “multilayer” is possible only if the pores are filled from the bottom up. For this nonlimiting, illustrative method of NRI and/or opto-magnetic material, fabrication is possible even if the pore walls are covered by insulating material since the pores are open from both ends and the current can pass through the electrolyte filling the pores during the plating process. Alternatively, the pores can be filled by an electroless plating process. In this case, no metal “multilayer” formation is possible. Other metal deposition processes (such as various modifications of Chemical Vapor Deposition) are also possible. It should be also noted that after both the electroplating and electroless-plating processes, some excessive metal can be formed on the first and/or second surfaces of the semiconductor wafer which may degrade the performance of the NRI and/or opto-magnetic material. Said excessive metal can be removed from the first surface of the semiconductor wafer by a chemical-mechanical polishing technique or any other removal technique known to those skilled in the art.
According to a further illustrative non-limiting method of manufacturing a NRI and/or opto-magnetic material of the second exemplary implementation of the present exemplary illustrative non-limiting implementation can be produced by:                starting with a semiconductor wafer having first and second surfaces, wherein said first surface is substantially flat,        Producing etch starting points on the first surface of the semiconductor wafer,        producing a porous layer in said wafer starting from the first surface,        coating the pore walls with metal-dielectric multilayer.        
The porous layer can be formed as was described in relation to illustrative methods of manufacturing an NRI and/or opto-magnetic material given previously.
Said coating of the pore walls with metal-dielectric multilayer structure can be done by means of the different variations of a Chemical Vapor Deposition (CVD) technique or by means of a combination of thermal oxidation with a CVD technique. Particularly, a combination of thermal oxidation with Metallo-Organic CVD (MOCVD) would be the technique of choice if the desired metal-dielectric multilayer by design should consist of just two layers, an insulating dielectric on the pore walls and a plasmon-supportive metal covering the dielectric. If more than two layers need to be employed (such as dielectric-metal-dielectric, or even more complex structure with several layers of metal and dielectric employed), Atomic Layer Deposition (ALD) would be the technique of choice to be used since it is better suited for uniform, pinhole-free covering of high aspect-ratio structures with multilayers, with excellent control over each layer thickness ([M. Ritala and M. Leskela, in: H. S. Nalwa, (Ed), Handbook of Thin Film Materials, Academic Press, San Diego, 2001, Vol. 1, Chapter 2, p 103], [S. M. George, A. W. Ott and J. W. Klaus, J. Phys. Chem. 100 (1996) 13121], [O. Sneh, R. B. Clark-Phelps, A. R. Londergan, J. L. Winkler and T. E. Seidel, Thin Solid Films, 402/1-2 (2002) 248], [O. Sneh, Solid State Technology, November 2003, p. 22]).
According to another illustrative non-limiting method of manufacture, an NRI and/or opto-magnetic material of the second exemplary implementation of the present exemplary illustrative non-limiting implementation can be produced by:                starting with a semiconductor wafer having first and second surfaces, wherein said first surface is substantially flat,        Producing an etching starting points on the first surface of the semiconductor wafer,        producing a porous layer in said wafer starting from the first surface,        removing the unetched part of said wafer at the ends of the pores, and        coating the pore walls with metal-dielectric multilayer.        
All the fabrication steps can be performed as was described in relation to previously described illustrative methods of manufacturing an NRI and/or opto-magnetic material. However, such a sequence of steps might be advantageous for the case of the NRI and/or opto-magnetic material with a high number of layers in the “multilayer” coating of the pore walls, since having pores open on both sides makes gas flow (i.e., reagent flow in the CVD techniques) simpler. In the case of MOCVD used as a deposition technique, this would open the potential for fabricating deeper pore structures (i.e. thicker films of NRI and/or opto-magnetic material), while in the case of ALD it would shorten the processing time and will potentially lower consumption of chemicals.